> I'm working on connecting temp probesto a 16C84. One idea is to use
> a voltage controller oscillator and connect it to an I/O pin and
> determine the timing. Use an analog switch to multiplex the input
> and go through timing a high and low reference voltage to compensate
> for any temperature drift, etc. Perhaps there is an integrated A/D
> converter out there doing all the already?
What kind of temperature probe? Is it a thermistor, thermocouple,
RTD, or what?
and.. What kind of accuracy do you need?
I've built some simple temperature probes with a thermistor, a
resistor and a capacitor, and using timing to digitize the input
signal (ala' app note AN512) . There are a lot of pitfalls, but it
works. No A/D converters, no op amps, no analog stuff, just three
parts.
HOWEVER if you are a newbee I wouldn't recommend this as your first
project. Try something simple. Make a light light or a beeper honk.
p.s. There are no stupid newbies. Anyone who even consideres
learning about microcontrollers has to have a quick wit.
> p.s. There are no stupid newbies. Anyone who even
> considers learning about microcontrollers has to have
> a quick wit.
Yeah, but not quick enough to learn how to
>What kind of temperature probe? Is it a thermistor, thermocouple,
>RTD, or what?
An LM35... Originally I wanted to connect the sensor to an ICL7106 (A/D with
built-in display driver. I thought the LM35 would make the design much
easier (with the ICL7106).
>and.. What kind of accuracy do you need?
0.5 Celcius is just fine.
>HOWEVER if you are a newbee I wouldn't recommend this as your first
>project. Try something simple. Make a light light or a beeper honk.
:-) Got to learn somehow. I did programming with a C64 a long time ago and
I worked a bit with HC705 and HC11 3 or 4 years ago. I've looked at PIC's
when I couldn't find the HC705 version I needed to finish my project.
Housebuilding and marriage happened and it took me a few years to get back
into working with microcontrollers and doing electronic projects.
There are two projects in the making, the thermometer... an indoor outdoor
unit with min/max memory and a clock for the reception of the WWVB time signal.
Getting the light on the 7 segment display to shine will be my very first
project with the PIC, though :-)
>>What kind of temperature probe? Is it a thermistor, thermocouple,
>>RTD, or what?
>
>An LM35... Originally I wanted to connect the sensor to an ICL7106 (A/D
with
>built-in display driver. I thought the LM35 would make the design much
>easier (with the ICL7106).
>
>>and.. What kind of accuracy do you need?
>
>0.5 Celcius is just fine.
Hey, this sounds familiar, I too am creating a thermometer as my first
project, but I'm making it handheld. If are looking for a temperature sensor
for connecting to a PIC, after thinking of using the LM35 I stubled on the
LM75, it saved me alot of work. It is a celcius temperature sensor, 0.5
degree resolution. This all sounds pretty much the same as the LM35 right?
Well, here is the kicker, it has an A/D convertor on board and a IC2
interface!! No further A/D conversion needed, no analog noise problems
between the PIC and the sensor, a two wire interface! Wow. Just thought you
should know, I certainly am using it. TTYL
Adi, I've used the LM34 (F vs C) in several applications. I'd recommend
using a 16C71 with it's 8-Bit A/Ds. If you have to use a 16x84, there are
several A/Ds with a 3-wire interface. I have a project where I use a MAX186
12-Bit, 8-channel, A/D. This has a 3-wire interface. Five channels are
assigned to 5 temperature zones, 2 for indoor and outdoor humidity, and 1
for barometric pressure. Though I use a 16C74 in this case, you can easily
interface it to a 16x84.
>>What kind of temperature probe? Is it a thermistor, thermocouple,
>>RTD, or what?
>
>An LM35... Originally I wanted to connect the sensor to an ICL7106 (A/D with
>built-in display driver. I thought the LM35 would make the design much
>easier (with the ICL7106).
>
>>and.. What kind of accuracy do you need?
>
>0.5 Celcius is just fine.
>
>>HOWEVER if you are a newbee I wouldn't recommend this as your first
>>project. Try something simple. Make a light light or a beeper honk.
>
>:-) Got to learn somehow. I did programming with a C64 a long time ago and
>I worked a bit with HC705 and HC11 3 or 4 years ago. I've looked at PIC's
>when I couldn't find the HC705 version I needed to finish my project.
>Housebuilding and marriage happened and it took me a few years to get back
>into working with microcontrollers and doing electronic projects.
>
>There are two projects in the making, the thermometer... an indoor outdoor
>unit with min/max memory and a clock for the reception of the WWVB time signal.
>
>Getting the light on the 7 segment display to shine will be my very first
>project with the PIC, though :-)
>
>Regards,
>Adi
>
>
The problem with the LM75 is the number of pins required to make it work.
At least one of my sensors in connected remotely. Running 2 wires, 3 wires
at the most is my goal. Still, the LM75 is a pretty interesting device!
Thanks,
Adi
----------
> From: Herbert Graf <.....hgrafKILLspam.....GEOCITIES.COM>
> To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU
> Subject: Re: (not so) stupid newbie
> Date: October 8, 1997 21:25 PM
> Hey, this sounds familiar, I too am creating a thermometer as my
first
> project, but I'm making it handheld. If are looking for a temperature
sensor
> for connecting to a PIC, after thinking of using the LM35 I stubled on
the
> LM75, it saved me alot of work. It is a celcius temperature sensor, 0.5
> degree resolution. This all sounds pretty much the same as the LM35
right?
> Well, here is the kicker, it has an A/D convertor on board and a IC2
> interface!! No further A/D conversion needed, no analog noise problems
> between the PIC and the sensor, a two wire interface! Wow. Just thought
you
> should know, I certainly am using it. TTYL
Tom, thanks you for the suggestions. I'll be getting the datasheet on the
MAX186... Do you have any suggestions for driving a display? I am wondering
if I should use I/O pins to multiplex LED's or if I am better of using a
disply driver with a serial interface? Another idea would be to connect a
shift register to a couple of I/O pins and use it to drive the segments and
use other I/O pins to drive the common cathode or anodes of the LED's...
What's a good way to finding and sourcing components? I used to use
databooks but my books are getting old (1987-1993 versions) and I find a
lot of devices are obsolete or not covered. Manufacturers websites are
great for datasheets but I need to have a pretty small selection of devices
or browsing through datasheets is getting quite time consuming...
Regards,
Adi
----------
> From: Tom Handley <thandleyspam_OUTTELEPORT.COM>
> To: @spam@PICLISTKILLspamMITVMA.MIT.EDU
> Subject: Re: (not so) stupid newbie
> Date: October 9, 1997 10:51 AM
>
> Adi, I've used the LM34 (F vs C) in several applications. I'd
recommend
> using a 16C71 with it's 8-Bit A/Ds. If you have to use a 16x84, there are
> several A/Ds with a 3-wire interface. I have a project where I use a
MAX186
> 12-Bit, 8-channel, A/D. This has a 3-wire interface. Five channels are
> assigned to 5 temperature zones, 2 for indoor and outdoor humidity, and 1
> for barometric pressure. Though I use a 16C74 in this case, you can
easily
> interface it to a 16x84.
>
> - Tom
On Thu, 9 Oct 1997 08:51:44 -0700 Tom Handley <KILLspamthandleyKILLspamTELEPORT.COM>
writes:
> Adi, I've used the LM34 (F vs C) in several applications. I'd
>recommend
>using a 16C71 with it's 8-Bit A/Ds. If you have to use a 16x84, there
>are
>several A/Ds with a 3-wire interface. I have a project where I use a
>MAX186
>12-Bit, 8-channel, A/D. This has a 3-wire interface. Five channels are
>assigned to 5 temperature zones, 2 for indoor and outdoor humidity,
>and 1
>for barometric pressure. Though I use a 16C74 in this case, you can
>easily
>interface it to a 16x84.
>
Tom,
I would be most appreciative if you would tell us what barometric
pressure sensor
you are using .
>Hi!
>
>The problem with the LM75 is the number of pins required to make it work.
>At least one of my sensors in connected remotely. Running 2 wires, 3 wires
>at the most is my goal. Still, the LM75 is a pretty interesting device!
Well, you could run 3 wires and power it remotely, a 9V battery would
probably last a very long time since the LM75 also has a sleep mode. TTYL
Adi, there are a lot of ways to drive the led displays and there are
variety of digital and analog temperature sensors. I assume you are going to
use a 16C/F84 since it's easy and cheap to program. Considering your
indoor/outdoor thermometer, I'd assume 2 or 3 digits for display and you are
using an LM35 sensor. You only need an 8-Bit A/D in this case. There are
other A/D techniques but I prefer a seperate A/D block. One 8-Bit A/D you
might consider is a National ADC0832 2-channel A/D with a serial interface.
You would normally use 4 lines to communicate with it. This leaves 9 lines
for the displays so you could drive a multiplexed 2 digit display directly.
It is possible to combine the Data In/Out lines of the ADC0832 so you could
free up another line and use a 3 digit display. You can also use LED driver
such as the MAX7219 which drives up to 8 digits using a 3-wire interface.
There are many ways to tackle this project and this is just one. Note, if
you decide to get a programmer that supports chips such as the 16C71 as well
as a UV chip eraser, then you can use the 16C71's analog inputs instead of
an external A/D.
For parts, here are some of the distributors I use in the US:
Digikey : 800-344-4539 http://www.digikey.com
Extensive line of parts. Stocks most of the PIC line.
Quick to stock new PICs. Excellent service.
Jameco : 800-831-4242 http://www.jameco.com
Variety of parts. Some of the PIC line. Good prices.
JDR : 800-538-5000 http://www.jdr.com
Variety of parts. Some of the PIC line. Good prices.
B.G. Micro: 800-276-2206 http://www.bgmicro.com
Many surplus and unique parts. Good prices. Very low
cost LCD displays for prototyping. ie: Optrex DMC20434
20x4 line display = $8.95. DMC16205 16x2/backlit = $10.99
>Tom, thanks you for the suggestions. I'll be getting the datasheet on the
>MAX186... Do you have any suggestions for driving a display? I am wondering
>if I should use I/O pins to multiplex LED's or if I am better of using a
>disply driver with a serial interface? Another idea would be to connect a
>shift register to a couple of I/O pins and use it to drive the segments and
>use other I/O pins to drive the common cathode or anodes of the LED's...
>
>What's a good way to finding and sourcing components? I used to use
>databooks but my books are getting old (1987-1993 versions) and I find a
>lot of devices are obsolete or not covered. Manufacturers websites are
>great for datasheets but I need to have a pretty small selection of devices
>or browsing through datasheets is getting quite time consuming...
>
>Regards,
>Adi
SL.LAKEHEADU.CA>
